The fire, which has burned 700 hectares, jumped the main road into Kurri Kurri just after noon.

The "Thor" water-bombing aircraft, three helicopters and 90 firefighters fought the blaze but it wasn't enough to prevent the heritage-listed Richmond Vale Railway Museum from suffering about $1 million in damage.

"There's a lot of stuff that was historically significant to this area that is now just gone," museum chairman Peter Meddows said.

"An 1880 restored coal hopper is now just ashes.

"It's a bit heartbreaking."

Mr Meddows said he was cut off from the museum by the fire but reached it later in the afternoon.

"It was total devastation, there was smoke, things smouldering," he said.

"We'll keep going, there's no doubt about that, it's just going to take us time to recover."

A fire near Black Hill, east of Kurri Kurri, forced the evacuation of Black Hill Public School.

"Due to the efforts of all involved during the day, we were able to manage these fires through difficult fire weather conditions," RFS incident controller superintendent Paul Jones said.

Watch and act alerts remain in place for fires at Woodlands, south of Batemans Bay in the south coast, and Tuncurry.

Meanwhile, in Sydney, RFS units fought a blaze at Beacon Hill which began on Tuesday and flared up again.

A man was charged with lighting a blaze in Sydney's north in bushland off the Berowra track.

Police allege they spotted the 50-year-old near a fire on Wednesday morning and caught him after he ran away.

He is expected to face Hornsby local court on Thursday over the fire and two others allegedly lit on September 5 and August 24.

The RFS says the NSW Far North Coast, North Coast, Greater Hunter and New England regions remain a very high fire risk on Thursday.

NOTE: News bulletins cannot be streamed due to IOC regulations, so you'll hear a message at these times. To resume our regular streaming programming, press Pause and then Play about 5 minutes past the hour.